UPDATE: FORT HOOD, Texas (CNN) -- Officers raided the apartment of the soldier suspected in the mass shooting at Fort Hood in Texas early Friday searching for clues to what caused the military psychiatrist to gun down soldiers he had taken an oath to help, a police spokeswoman said.
The alleged gunman, identified as Maj. Nidal Malik Hasan, opened fire at a military processing center at Fort Hood, killing 13 and wounding 30 others, a military spokesman said.
Hasan, a psychiatrist practicing at Darnall Army Medical Center at Fort Hood, was shot multiple times and was taken into custody ending the shooting rampage Thursday afternoon, Lt. Gen. Robert Cone said.
In the nearby town of Killeen, a police SWAT team and FBI agents were searching Hasan's apartment to help determine what caused the shooting military experts called the worst mass shooting at an American military base, Carol Smith, a Killeen police spokeswoman, said early Friday.
And as investigators gathered evidence, details began to emerge about the alleged shooter.
Hasan, 39, is a graduate of Virginia Tech and a psychiatrist licensed in Virginia who previously worked at Walter Reed Army Medical Center.
A federal official said Hasan is a U.S. citizen of Jordanian descent. Military documents show that Hasan was born in Virginia, and has never deployed outside the United States.
Sen. Kay Bailey Hutchison, R-Texas, said Friday that investigators were still trying to determine a motive,
"But since he is alive, certainly we will learn much more when he is able to be interrogated," she said. "But of course, the fact that he was getting ready to be deployed and certainly had this history of talking to people who have come back begins to form a picture."
An owner of a 7-Eleven convenience store in Fort Hood said Hasan -- whom he knows as "Major Nidal" -- came in for coffee and hash browns most mornings, including the morning of the shootings.
Surveillance video from the store obtained by CNN shows a man who according to the store owner is Hasan at the cashier's counter at about 6:20 a.m. Thursday -- about seven hours before the mass shooting -- carrying a beverage and dressed in traditional Arab garb.
"He looked normal, came in had his hash browns and coffee as you see in the surveillance video," the owner told CNN.
Other surveillance footage from Tuesday showed him wearing hospital scrubs.
Hasan's first cousin, Nader Hasan, issued a statement late Thursday on behalf of their family, saying they are "shocked and saddened" by the shootings.
"We are filled with grief for the families of today's victims," the statement says. "Our family loves America. We are proud of our country, and saddened by today's tragedy. Because this situation is still unfolding, we have nothing else that we are able to share with you at this time."
The shooting occurred in a building called the readiness center, one of the last stops before they deploy and one of the first places a soldier goes upon returning to the United States.
Some of the victims were headed to Iraq or Afghanistan, said Col. Benton Danner.
At a news conference earlier in the day, Cone said the shooter had two handguns, one of them a semi-automatic.
"All the casualties took place at the initial incident, that took place at 13:30, at the soldier readiness facility," Cone said, referring in military time to 1:30 p.m.
A witness in a building adjacent to where the shooting happened said soldiers were cutting up their uniforms into homemade bandages as the wounded were brought into the building.
"It was total chaos," the witness said.
Cone noted that a graduation ceremony was being held in an auditorium about 50 yards away from where the shooting took place.
"Thanks to the quick reaction of several soldiers, they were able to close off the doors to that auditorium where there were some 600 people inside," he said.
President Barack Obama called the shootings "tragic" and "a horrific outburst of violence." White House spokesman Robert Gibbs said earlier that officials were monitoring the incident in the Situation Room. The Department of Homeland Security said it was in the process of obtaining information.
Adm. Michael Mullen, chairman of the Joint Chiefs of Staff, has been informed as well, and is "greatly disturbed" about the incident, his spokesman told CNN.
Texas Gov. Rick Perry ordered that all flags in the state be lowered to half-staff until Sunday as a tribute to the victims.
"We are deeply saddened by today's events, but resolve to continue supporting our troops and protecting our citizens," he said.
In the aftermath of the incident, Scott & White Memorial Hospital in Temple, Texas, posted an online appeal for blood as it began receiving victims. "Due to the recent events on Fort Hood, we are in URGENT need of ALL blood types," it said.
Fort Hood is the Army's largest U.S. post, with about 40,000 troops stationed there. It is home to the Army's 1st Cavalry Division and elements of the 4th Infantry Division, as well as the 3rd Armored Cavalry Regiment and the 13th Corps Support Command. It is located near Killeen, Texas. The Headquarters Unit and three brigades of the 1st Cavalry are currently deployed in Iraq.
The fort is home to the Warrior Combat Stress Reset Program, which helps soldiers returning from war with combat stress and Post Traumatic Stress Disorder.
In June, Fort Hood's commander, Lt. Gen. Rick Lynch, told CNN that he was trying to ease the kind of stresses soldiers face. He has pushed for soldiers working a day schedule to return home for dinner by 6 p.m., and required his personal authorization for anyone working weekends. At the time, two soldiers stationed there had committed suicide in 2009 -- a rate well below those of other posts.
Nearby Killeen was the scene of one of the most deadly shootings in American history 18 years ago when George Hennard crashed his truck into a Luby's Cafeteria and then began shooting, killing 23 people and wounding 20.
Hennard's spree lasted 14 minutes. He eventually took his own life.